Response of lysozyme internal dynamics to hydration probed by13C and1H solid-state NMR relaxation
Response of lysozyme internal dynamics to hydration probed by13C and1H solid-state NMR relaxation
复制标题
通过 13C 和 1H 固态 NMR 弛豫探测溶菌酶内部动力学对水合的响应
DOI：
10.1007/bf03166746
复制
发表时间：
2004
影响因子：
1
通讯作者：
D. Reichert
中科院分区：
文献类型：
--
作者：
A. Krushelnitsky;D. Reichert
利用天然丰富的13c和1h核磁共振（NMR）弛豫研究了蛋清溶菌酶内部蛋白质动力学的水合依赖性。在0 ~ 50℃的温度范围内测量了核磁共振弛豫时间st1、非共振时间et1p和质子解耦的非共振时间et1p（仅用于碳实验）。碳交叉极化魔角旋转光谱的光谱分辨率允许对甲基碳、亚甲基碳和甲基碳分别进行处理，而质子实验一次只能从所有质子中获得一个积分信号。利用已建立的相关函数形式化方法和无模型方法定量分析了弛豫时间。假设三种运动类型的相关时间分别为10−4秒、10−9秒和10−12秒，可以用一个模型充分描述整个数据集。最慢的过程是不同能量最小值之间的相关构象跃迁，中间过程可以确定为在一个能量最小值内的振动，最快的过程是甲基质子在甲基对称轴上的快速旋转。先前的一项研究（A. Krushelnitsky， D. Faizullin， D. Reichert, Biopolymers 73, 1-15, 2004）对溶菌酶和聚赖氨酸的动态行为进行了比较，结果表明，在干燥状态下，这两种生物聚合物在快、慢时间尺度上都是刚性的。在水合作用下，溶菌酶和聚赖氨酸显示出相当大的内部流动性增强，然而，以不同的方式。聚赖氨酸的侧链比溶菌酶的侧链更容易移动，而主链则相反。这种差异与溶菌酶和聚赖氨酸的结构特征有关。由于存在快速自旋扩散，质子弛豫数据的分析是一项更加困难的任务。然而，我们的数据表明，从碳和质子实验得到的运动相关函数有本质上的不同。我们用这两种核磁共振弛豫实验探测不同核间矢量的运动来解释这一点。将质子弛豫时间st1与我们之前在宽温度范围内测量的质子弛豫时间st1的结果进行比较，表明在低温溶菌酶发生结构重排，影响运动的振幅和/或活化能。
We have studied the hydration dependence of the internal protein dynamics of hen egg white lysozyme by naturally abundant13C and1H nuclear magnetic resonance (NMR) relaxation. NMR relaxation timesT1, off-resonanceT1p and proton-decoupled on-resonanceT1p (only for carbon expriments) were measured in the temperature range from 0 to 50°C. The spectral resolution in carbon cross-polarization magic angle spinning spectrum allows to treat methine, methylene and methyl carbons separately, while proton experiments provide only one integral signal from all protons at a time. The relaxation times were quantitatively analyzed by the well-established correlation function formalism and model-free approach. The whole set of the data could be adequately described by a model assuming three types of motion having correlation times around 10−4, 10−9 and 10−12 s. The slowest process originated from correlated conformational transitions between different energy minima, the intermediate process could be identified as librations within one energy minimum, and the fastest one is a fast rotation of methyl protons the symmetry axis of methyl groups. A comparison of the dynamic behavior of lysozyme and polylysine obtained from a previous study (A. Krushelnitsky, D. Faizullin, D. Reichert, Biopolymers 73, 1–15, 2004) reveals that in the dry state both biopolymers are rigid on both fast and slow time scales. Upon hydration, lysozyme and polylysine reveal a considerable enhancement of the internal mobility, however, in different ways. The side chains of polylysine are more mobile than those of lysozyme, whereas for the backbone a reversed picture is observed. This difference correlates with structural features of lysozyme and polylysine discussed in detail. Due to the presence of a fast spin diffusion, the analysis of proton relaxation data is a more difficult task. However, our data demonstrate that the correlation functions of motion obtained from carbon and proton experiments are substantially different. We explained this by the fact that these two types of NMR relaxation experiments probe the motion of different internuclear vectors. The comparison of the proton data with our previous results on proton relaxation timesT1 measured over a wide temperature range indicates that at low temperatures lysozyme undergoes structural rearrangements affecting the amplitudes and/or activation energies of motions.